US6954095B2 - Apparatus and method for generating clock signals - Google Patents
Apparatus and method for generating clock signals Download PDFInfo
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- US6954095B2 US6954095B2 US10/807,003 US80700304A US6954095B2 US 6954095 B2 US6954095 B2 US 6954095B2 US 80700304 A US80700304 A US 80700304A US 6954095 B2 US6954095 B2 US 6954095B2
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- locked loop
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C7/00—Arrangements for writing information into, or reading information out from, a digital store
- G11C7/22—Read-write [R-W] timing or clocking circuits; Read-write [R-W] control signal generators or management
- G11C7/222—Clock generating, synchronizing or distributing circuits within memory device
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11C—STATIC STORES
- G11C7/00—Arrangements for writing information into, or reading information out from, a digital store
- G11C7/22—Read-write [R-W] timing or clocking circuits; Read-write [R-W] control signal generators or management
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION, OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
- H03L7/00—Automatic control of frequency or phase; Synchronisation
- H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
- H03L7/08—Details of the phase-locked loop
- H03L7/081—Details of the phase-locked loop provided with an additional controlled phase shifter
- H03L7/0812—Details of the phase-locked loop provided with an additional controlled phase shifter and where no voltage or current controlled oscillator is used
Definitions
- the phase detector is an integration sampler to integrate the first clock signal against the reference clock signal.
- FIG. 3 illustrates a circuit capable of generating the T-CLK and R-CLK signals shown in FIG. 2 .
- the output of delay circuit 212 is coupled to a clock buffer 216 , the output of which is the R-CLK signal.
- the R-CLK signal is provided to an integration sampler 222 .
- the output of the 180 degree phase shift circuit 210 is coupled to another clock buffer 214 , the output of which is the T-CLK signal.
- the T-CLK signal is provided to the output driver 220 and delay circuit 218 .
- the 180 degree phase shift circuit 210 reverses the two clock signal conductors, thereby shifting the phase of the clock signal by 180 degrees. This 180 degree phase shift is necessary to maintain the relationship between the odd data and the even data (see FIG. 2 ), where odd data is sampled on the rising edge of the clock signal and the even data is sampled on the falling edge of the clock signal.
- the integration sampler 204 begins sampling the value of the even data on the rising edge of R-CLK and continues sampling and integrating the sampled values until the falling edge of R-CLK. When the falling edge of R-CLK is reached, the integration sampler 204 determines the value of the data sampled, i.e., a logic “1” or “0”. Next, the integration sampler 204 begins sampling the value of the odd data on the falling edge of R-CLK and continues sampling and integrating the sampled values until the rising edge of R-CLK. At this point, the integration sampler 204 determines whether a logic “1” or a logic “0” was sampled. The integration sampler 204 then begins sampling the value of the even data, and repeats this cycle of alternating between sampling of even data and odd data.
Abstract
A delay-locked loop circuit generates a first clock signal. The delay-locked loop circuit includes a first delay element coupled in a feedback path of the delay-locked loop circuit to advance the first clock signal relative to a reference clock signal by a first time period. A second delay element is coupled to receive the first clock signal from the delay-locked loop circuit. The second delay element also outputs a second clock signal that is delayed relative to the first clock signal by the first time period. The delay-locked loop circuit may include a phase detector to identify phase differences between the first clock signal and the reference clock signal. A third delay element may be coupled between the delay-locked loop circuit and the second delay element.
Description
This continuation application claims priority to application Ser. No. 10/158,505 U.S. Pat. No. 6,731,148 to Benedict C. Lau et al., filed May 29, 2002, entitled “Apparatus and Method for Generating Clock Signals, which in turn is a continuation of appl. No. 09/642,484 and claims priority to U.S. Pat. No. 6,469,555 to the same inventors, filed Aug.18, 2000, entitled “Apparatus and Method for Generating Multiple Clock Signals from A Single Loop Circuit.”
The present invention relates to clock circuitry and, more particularly, to methods and circuits that generate clock signals indicating when to read and write data on a bus.
Clock signals are used in electrical circuits to control the flow of data on data communication busses and control the timing and processing of various functions. In particular systems, data is written to a data bus or read from the data bus based on the state of one or more clock signals. These clock signals are necessary to prevent “collision” of data, i.e., the simultaneous transmission of data by two different devices on the same data bus. The clock signals also ensure that the desired data is available on the data bus when read by a device.
As shown in FIG. 2 , the R-CLK signal is adjusted to account for the setup time (Tsu) necessary to communicate the appropriate data to the data bus. To ensure that the edge of BUS CLK aligns with the center of the available data, the 90 degree center point of the data on the data bus must be Tsu seconds before the corresponding sampling edge of the internal R-CLK.
The circuit described above with respect to FIG. 3 requires two separate delay-locked loops to generate the R-CLK and the T-CLK signals. The use of two delay-locked loops requires a significant amount of power and uses a significant amount of layout area within the memory controller.
An improved architecture described herein addresses these and other problems by simplifying the circuit that generates the R-CLK and the T-CLK signals.
The improved architecture discussed below generates the R-CLK and T-CLK signals using a single delay-locked loop. The use of a single delay-locked loop requires fewer components and reduces the power consumption of the circuit as compared to the circuit described above in FIG. 3. Additionally, the improved architecture requires less area within the memory controller.
In one embodiment, a delay-locked loop circuit generates a first clock signal. The delay-locked loop circuit includes a first delay element coupled in a feedback path of the delay-locked loop circuit to advance the first clock signal relative to a reference clock signal by a first time period. A second delay element is coupled to receive the first clock signal from the delay-locked loop circuit and to output a second clock signal that is delayed relative to the first clock signal by the first time period.
In another embodiment, the delay-locked loop circuit further includes a phase detector to identify phase differences between the first clock signal and the reference clock signal.
In one embodiment, the phase detector is an integration sampler to integrate the first clock signal against the reference clock signal.
In a described implementation, the delay-locked loop circuit includes a 180 degree phase shifter to adjust the phase of the first clock signal.
In a particular embodiment, a third delay element is coupled between the delay-locked loop circuit and the second delay element.
An improved architecture is discussed herein for generating the R-CLK and T-CLK signals using a single delay-locked loop. The use of a single delay-locked loop requires fewer components, reduces the power consumption of the circuit, and requires less layout area within the memory controller.
The output of delay circuit 212 is coupled to a clock buffer 216, the output of which is the R-CLK signal. The R-CLK signal is provided to an integration sampler 222. The output of the 180 degree phase shift circuit 210 is coupled to another clock buffer 214, the output of which is the T-CLK signal. The T-CLK signal is provided to the output driver 220 and delay circuit 218.
Since the clock signal is created and transmitted differentially, the 180 degree phase shift circuit 210 reverses the two clock signal conductors, thereby shifting the phase of the clock signal by 180 degrees. This 180 degree phase shift is necessary to maintain the relationship between the odd data and the even data (see FIG. 2), where odd data is sampled on the rising edge of the clock signal and the even data is sampled on the falling edge of the clock signal.
A delay-locked loop circuit is formed by fine loop circuit 208, 180 degree phase shift circuit 210, clock buffer 214, delay circuit 218, and integration sampler 204. The delay circuit 218 compensates for the delay caused by the output driver 220. The output of delay circuit 218 is provided to the integration sampler 204, the operation of which is discussed below. Since the delay circuit 218 is located in the feedback path of the delay-locked loop circuit, the delay caused by delay circuit 218 causes fine loop circuit 208 to advance the clock signal (T-CLK) relative to the reference clock signal (i.e., BUS CLK). The clock signal is advanced by a period equal to the delay caused by delay circuit 218.
Thus, as shown in FIG. 4 , the circuit 200 includes a single delay-locked loop, created by fine loop 208, 180 degree phase shift circuit 210, clock buffer 214, delay circuit 218, and integration sampler 204. Since delay-locked loops consume a significant amount of power, the use of a single delay-locked loop (rather than multiple delay-locked loops) significantly reduces the power consumption of the memory controller.
Along the first path, the clock signal is phase shifted by 180 degrees (block 324) and buffered (block 326). After buffering the clock signal, the procedure outputs the T-CLK signal (block 328) and provides the same clock signal to a block that delays the clock signal (block 330). The clock signal is delayed to compensate for the delay caused by the output buffer. Next, the delayed clock signal is integrated using an integration sampler (step 332). The integration results are provided back to block 322, which adjusts the incoming bus clock signal based on the integration results.
Along the second path, the clock signal is delayed (block 334) to compensate for the delay caused by the output driver in making data available on the data bus. Next, the delayed clock signal is buffered (block 336) and the procedure outputs the R-CLK signal (block 338), for example to an integration sampler. Thus, the procedure 315 shown in FIG. 7 generates both the T-CLK and the R-CLK signals from a single bus clock signal. In a particular embodiment of procedure 315, delays associated with blocks 328, 330, and 334 are approximately equal. Similarly, delays associated with blocks 326 and 336 are approximately equal.
In an alternate embodiment, the integration sampler 204 shown in FIG. 4 can be implemented as a quadrature phase detector.
A fine loop 458 receives signals from the reference loop 456 and the zero phase detector 454. Fine loop 458 outputs a signal to a 180 degree phase shifter 460 and a clock buffer 470. The phase-shifted signal generated by phase shifter 460 is provided to a Tod delay circuit 462 and continues to a clock buffer 464. The output of clock buffer 464 is the R-CLK signal. The output of the clock buffer is provided to the zero phase detector 454 and an integration sampler 466, which receives data from a data bus 468. Thus, a delay-locked loop is created by fine loop 458, 180 degree phase shift circuit 460, Tod delay circuit 462, clock buffer 464, and zero phase detector 454.
The clock buffer 470 provides a buffered output signal to a pair of output drivers 472 and 474, each of which include a Tod delay. The output signal provided from the clock buffer 470 to output driver 474 is the T-CLK signal. Output driver 472 generates a CFM signal and output driver 474 provides an output signal to the data bus 468.
A clock amplifier 502 and a zero phase detector receive the CTM clock signal. The output of clock amplifier 502 is provided to a reference loop 506. A fine loop 508 receives signals from the reference loop 506 and the zero phase detector 504. The output generated by fine loop 508 is provided to a clock buffer 510. The output of the clock buffer 510 is the T-CLK signal, which is the same as the R-CLK signal in this circuit 500. The output of the clock buffer 510 is provided to the zero phase detector 504, an integration sampler 512, and a pair of output drivers 516 and 518. The integration sampler 512 receives data from a data bus 514. Output driver 516 provides its output to data bus 514 and output driver 518 generates a CFM clock signal.
Thus, a system has been described that generates multiple clock signals from a single bus clock signal. The described system uses a single delay-locked loop to generate the multiple clock signals. Using a single delay-locked loop reduces the number of components in the system, reduces the circuit's power consumption, and requires a smaller layout area within the memory controller or other device.
Although the description above uses language that is specific to structural features and/or methodological acts, it is to be understood that the invention defined in the appended claims is not limited to the specific features or acts described. Rather, the specific features and acts are disclosed as exemplary forms of implementing the invention.
Claims (37)
1. A system, comprising:
a random access memory device;
a first signal line coupled to the random access memory device, the first signal line to carry a first signal;
a second signal line coupled to the random access memory device, the second signal line to carry a second signal; and
a memory controller coupled to the first signal line and the second signal line, wherein the memory controller includes a delay locked loop to generate the first signal, wherein the first signal is used to transmit data to the random access memory device, the delay locked loop to receive the second signal such that the second signal is used to sample read data provided by the memory device.
2. The system as recited in claim 1 , wherein the memory controller includes a driver such that the first signal is used to transmit data to the memory device by way of the driver.
3. The system as recited in 1, wherein the memory controller includes a sampler to sample the read data using the second signal.
4. The system as recited in claim 4 , further comprising:
a first delay element coupled in a feedback path of the delay-locked loop to change a phase difference between the second signal and a reference clock signal by a first time period.
5. The system as recited in claim 4 , further comprising:
a second delay element outside the feedback path of the delay-locked loop
to receive the second signal, and
to delay the first signal relative to the second signal by the first time period.
6. The system of claim 1 , further including a clock generator to generate the second signal, wherein the second signal propagates from the clock generator to the memory controller.
7. The system of claim 6 , wherein the second signal is terminated after being received by the memory controller.
8. The system of claim 1 , wherein the first signal is a clock signal and the second signal is a clock signal.
9. The system as recited in claim 1 , wherein the delay-locked loop further includes a phase detector to identify phase differences between the second signal and the reference clock signal.
10. The system as recited in claim 9 , wherein the phase detector is a zero phase detector.
11. The system as recited in claim 9 , wherein the phase detector is an integration sampler to integrate the first signal with respect to the reference clock signal.
12. The system as recited in claim 1 , wherein the delay-locked loop further includes a 180 degree phase shift circuit to adjust a phase of the second signal.
13. The system as recited in claim 12 , wherein the 180 degree phase shift is accomplished by switching over the first signal line and the second signal line.
14. The system as recited in claim 1 , wherein first data of the read data is sampled on a rising edge of the second signal and second data of the read data is sampled on a falling edge of the second signal.
15. The system as recited in claim 1 , wherein the delay lock loop generates a receive clock using the second signal, wherein the receive clock is used to sample read data by way of the second signal.
16. The system of claim 15 , wherein the delay locked loop generates the receive clock such that a phase of the receive clock is aligned with a phase of the second signal.
17. A method of operation in a memory controller comprising:
generating a first signal using a single delay-locked loop wherein the first signal is used to time data transmission;
changing a phase difference between the first signal and a reference signal by a first time period using a second delay element outside the feedback path of the delay-locked loop circuit; and
receiving a second signal to be delayed relative to the first signal by the first time period using a first delay element in a feedback path of the delay-locked loop, wherein the second signal is used to time data reception.
18. The method as recited in claim 17 , further comprising transmitting data by way of a driver.
19. The method as recited in 17, further comprising sampling the read data using the second signal.
20. The method as recited in claim 17 , further comprising changing a phase difference between the second signal and a reference clock signal by a first time period.
21. The method as recited in claim 20 , further comprising delaying the first signal relative to the second signal by the first time period.
22. The method of claim 17 , further comprising generating the second signal from a clock generator and propagating the second signal to a memory controller.
23. The method of claim 22 , further comprising terminating the second signal after the second signal is received by the memory controller.
24. The method of claim 17 , wherein the first signal is a clock signal and the second signal is a clock signal.
25. The method as recited in claim 17 , further comprising identifying phase differences between the second signal and the reference clock signal.
26. The method as recited in claim 25 , further comprising detecting a zero phase difference.
27. The method as recited in claim 25 , further comprising integrating the first signal with respect to the reference clock signal.
28. The method as recited in claim 17 , further comprising adjusting a phase of the second signal by 180 degrees.
29. The method as recited in claim 28 , further comprising switching over the first signal line and the second signal line to effect the 180 degree phase shift.
30. The method as recited in claim 17 , wherein first data of the read data is sampled on a rising edge of the second signal and second data of the read data is sampled on a falling edge of the second signal.
31. The method as recited in claim 17 , further comprising generating a receive clock using the second signal, wherein the receive clock is used to sample read data by way of the second signal.
32. The method of claim 31 , further comprising generating the receive clock such that a phase of the receive clock is aligned with a phase of the second signal.
33. A system, comprising:
an electronic data store;
a controller for the electronic data store, including:
a delay-locked loop to receive a second signal, wherein the delay-locked loop includes:
a first delay element coupled in a feedback path of the delay-locked loop, wherein the first delay element changes a phase difference between the second signal and a reference clock signal by a first time period, and
a second delay element outside the feedback path to receive the second signal and output a first signal that is delayed relative to the second signal by the first time period, and
a phase detector to determine phase differences between the second signal and the reference clock signal.
34. The system as recited in claim 33 , wherein the phase detector comprises a zero phase detector.
35. The system as recited in claim 33 , wherein the delay-locked loop further includes a 180 degrees phase shifter.
36. The system as recited in claim 33 , wherein the first and second signals provide timing for address multiplexing operations of the electronic data store.
37. The system as recited in claim 33 , further comprising an integration sampler to integrate the first signal with respect to the reference clock signal.
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US10/807,003 US6954095B2 (en) | 2000-08-18 | 2004-03-22 | Apparatus and method for generating clock signals |
US11/192,584 US20050265117A1 (en) | 2000-08-18 | 2005-07-29 | Apparatus and method for generating clock signals |
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US09/642,484 US6469555B1 (en) | 2000-08-18 | 2000-08-18 | Apparatus and method for generating multiple clock signals from a single loop circuit |
US10/158,505 US6731148B2 (en) | 2000-08-18 | 2002-05-29 | Apparatus and method for generating clock signals |
US10/807,003 US6954095B2 (en) | 2000-08-18 | 2004-03-22 | Apparatus and method for generating clock signals |
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US10/158,505 Continuation US6731148B2 (en) | 2000-08-18 | 2002-05-29 | Apparatus and method for generating clock signals |
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US11/192,584 Continuation US20050265117A1 (en) | 2000-08-18 | 2005-07-29 | Apparatus and method for generating clock signals |
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US10/158,505 Expired - Lifetime US6731148B2 (en) | 2000-08-18 | 2002-05-29 | Apparatus and method for generating clock signals |
US10/807,003 Expired - Lifetime US6954095B2 (en) | 2000-08-18 | 2004-03-22 | Apparatus and method for generating clock signals |
US11/192,584 Abandoned US20050265117A1 (en) | 2000-08-18 | 2005-07-29 | Apparatus and method for generating clock signals |
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US10/158,505 Expired - Lifetime US6731148B2 (en) | 2000-08-18 | 2002-05-29 | Apparatus and method for generating clock signals |
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2000
- 2000-08-18 US US09/642,484 patent/US6469555B1/en not_active Expired - Lifetime
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2002
- 2002-05-29 US US10/158,505 patent/US6731148B2/en not_active Expired - Lifetime
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2004
- 2004-03-22 US US10/807,003 patent/US6954095B2/en not_active Expired - Lifetime
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2005
- 2005-07-29 US US11/192,584 patent/US20050265117A1/en not_active Abandoned
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Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
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US20050265117A1 (en) * | 2000-08-18 | 2005-12-01 | Rambus Inc. | Apparatus and method for generating clock signals |
US20070069782A1 (en) * | 2005-09-28 | 2007-03-29 | Hynix Semiconductor Inc | Delay locked loop for high speed semiconductor memory device |
US7365583B2 (en) | 2005-09-28 | 2008-04-29 | Hynix Semiconductor Inc. | Delay locked loop for high speed semiconductor memory device |
US20080164921A1 (en) * | 2005-09-28 | 2008-07-10 | Hynix Semiconductor Inc. | Delay locked loop for high speed semiconductor memory device |
US7649390B2 (en) | 2005-09-28 | 2010-01-19 | Hynix Semiconductor, Inc. | Delay locked loop for high speed semiconductor memory device |
US20070075758A1 (en) * | 2005-09-30 | 2007-04-05 | Alan Fiedler | Delay-locked loop |
US7285996B2 (en) | 2005-09-30 | 2007-10-23 | Slt Logic, Llc | Delay-locked loop |
US8791735B1 (en) * | 2013-04-03 | 2014-07-29 | Fujitsu Limited | Receiving circuit and control method of receiving circuit |
Also Published As
Publication number | Publication date |
---|---|
US20050265117A1 (en) | 2005-12-01 |
US20020140473A1 (en) | 2002-10-03 |
US6469555B1 (en) | 2002-10-22 |
US6731148B2 (en) | 2004-05-04 |
US20040174195A1 (en) | 2004-09-09 |
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